1. Field of the Invention
The present invention relates to recording method and apparatus using a process for communicating a bubble formed by utilizing thermal energy with atmosphere.
The present invention is applicable to printers for effecting the recording on a recording medium such as a paper sheet, a thread sheet, a fiber sheet, a cloth, a leather sheet, a metal sheet, a plastic sheet, glass, wood, ceramic sheet and the like, copying machines, facsimiles having a communication system, ETWs having keyboard input, and word processors, and to composite equipments.
Incidentally, in this specification and claims, a term xe2x80x9crecordingxe2x80x9d means not only application of a significant image such as a character or a figure onto a recording medium but also application of a meaningless image such as a pattern onto a recording medium.
2. Related Background Art
Regarding practical recording methods applicable to various recent printers, an ink jet system in which a liquid droplet is formed by using a bubble generated by film-boiling caused by thermal energy (as disclosed in U.S. Pat. Nos. 4,723,129 and 4,740,796) is effective. Further, U.S. Pat. No. 4,410,899 discloses a recording method in which a liquid passage is not closed or blocked during generation of a bubble.
Although the techniques disclosed in the above U.S. Patents can be applied to various recording systems, the above U.S. Patents do not disclose or teach application to a system in which the recording is effected by communicating a bubble generated with atmosphere. Such a system is referred to as xe2x80x9catmosphere communication systemxe2x80x9d or xe2x80x9catmosphere communication typexe2x80x9d hereinafter.
By the way, among the atmosphere communication system, an atmosphere communication system using rupture of the bubble does not provide stable liquid discharging, and, thus, is not practical.
Further, although a discharging principle is not known, a wishful phenomenon is disclosed in the Japanese Patent Application Laid-open No. 54-161935. In this technique, a cylindrical heater is disposed in each cylindrical nozzle so that the interior of the nozzle is divided into two by a bubble generated. In this arrangement, a liquid droplet can be formed, but, at the same time, a number of fine or minute liquid droplets are also formed due to xe2x80x9csplashxe2x80x9d.
The Japanese Patent Application Laid-open No. 5-16365 discloses the invention in which the atmosphere communication system is improved up to a practical level.
The invention disclosed in the above Japanese Patent Application Laid-open No. 5-16365 aims to communicate a bubble generated for discharging an ink droplet from a discharge nozzle with atmosphere outside of the discharge nozzle in the vicinity of the discharge outlet. In the above Japanese Patent Application Laid-open No. 5-16365, a position of a thermal energy generating means for generating the bubble and pressure of the generated bubble are regulated or selected, and various parameters for communicating the bubble with the atmosphere under the regulated conditions, kind of liquid, configuration of the discharge outlet and a drive condition for generating the thermal energy are concretely specified. And, with the arrangement as mentioned above, the liquid discharging can be achieved with a good re-filling feature and without generating the splash and ink mist, and a recording apparatus having good frequency response and capable of providing a high quality image can be obtained. Further, since the bubble generated for effecting the liquid discharging is communicated with the atmosphere during the liquid discharging operation, a waiting time for disappearing the bubble in the liquid is not required, thereby achieving the high speed recording.
On the other hand, regarding liquid discharging techniques in which a bubble is generated and then disappeared in a liquid passage, U.S. Pat. No. 4,638,337 discloses the fact that the bubble is communicated with atmosphere in a nozzle due to retardation of a part of meniscus into the nozzle, thereby causing inconvenience. Incidentally, the above U.S. Patent merely discloses the invention in which the bubble is surely generated and disappeared in the nozzle in order to eliminate a phenomenon that the bubble is communicated with the atmosphere in the nozzle due to the retardation of the meniscus into the nozzle.
Among the recording apparatuses of atmosphere communication type, in the recording apparatus disclosed in the above Japanese Patent Application Laid-open No. 54-161935, the discharging principle is not obvious, the practical level is not reached and it is difficult to put it to a practical use.
Although the invention disclosed in the above Japanese Patent Application Laid-open No. 5-16365 has the above-mentioned advantage, the following improvements may be desired to provide a recording apparatus having good frequency response and capable of obtaining a high quality image:
Firstly, since the bubble is grown outside of the discharge opening because a bubble generating portion is situated in the vicinity of the discharge opening, a volume of the liquid passage cannot be used effectively, with the result that a volume of the discharged liquid becomes smaller. This must be improved.
Secondly, since a bubble generating condition itself of the bubble generating portion for communicating the bubble with the atmosphere is greatly limited, an allowable design range of a recording head and kinds of liquids which can be used in the recording apparatus are also limited. This must be improved.
Thirdly, if the formation of the bubble is unstable in dependence upon change in environmental condition (for example, temperature, humidity and the like), since the unstable bubble formation directly affects an influence upon the communication between the bubble and the atmosphere, the unstable bubble formation affects an influence upon the discharged liquid (liquid droplet), thereby affecting an influence upon the recording. This should be improved.
Fourthly, regarding the discharging efficiency, there is energy loss. This should also be improved.
Lastly, since the re-filling feature cannot be improved, the frequency response is limited. This must be improved.
The present invention aims to eliminate the above-mentioned conventional drawbacks.
A first object of the present invention is to provide a liquid discharging system and a liquid discharging method, a liquid droplet discharging head used in such system and method, and a recording apparatus using such a discharging head, in which a condition that a bubble is communicated with atmosphere outside of a discharge opening is optimized while improving discharging efficiency, a discharging amount or a discharging speed.
A second object of the present invention is to provide a new liquid discharging head of atmosphere communication type which can eliminate the above-mentioned limitations in conventional liquid discharging heads of atmosphere communication type, can widen an allowable design range greatly and can discharge ink with high accuracy.
A third object of the present invention is to provide a liquid discharging method, a liquid droplet discharging head used in such system and method, and a recording apparatus using such a discharging head, which can eliminate limitation in the above-mentioned re-filling feature of conventional liquid discharging systems of atmosphere communication type, can improve a re-filling feature and can achieve high level frequency response.
A fourth object of the present invention is to permit the discharging of liquids in which deposit can easily be formed and/or suction discharge liquids.
In addition, a fifth object of the present invention is to provide a preserving method for maintaining reliability of a new liquid droplet discharging head capable of achieving at least one of the above objects for a long time.
The other objects of the present invention will be apparent from the following detailed explanation of the invention referring to the accompanying drawings.
According to the present invention, there is provided a discharging method for discharging liquid by communicating a bubble formed and grown in the liquid with atmosphere at an area of a discharge opening, comprising the step of causing displacement of a movable member having a free end for guiding the bubble toward the discharge opening while controlling the growth of the bubble, in accordance with the growth of the bubble.
In this case, in order to perform the re-filling of the liquid after the liquid discharging, when the bubble is communicated with the atmosphere, a liquid passage communicated with a liquid supply source to receive the liquid from the liquid supply source may not be blocked by the bubble.
Further, in order to prevent the scattering of the liquid during the liquid discharging, the bubble may be communicated with the atmosphere in a condition that inner pressure of the bubble is lower than the atmospheric pressure.
In addition, in order to reduce the inner pressure of the bubble below the atmospheric pressure during the communication between the bubble and the atmosphere, a heat generating element for generating the bubble in the liquid may be used, and the bubble generated in the liquid by the heat generating element may be communicated with the atmosphere through the discharge opening under a condition that a distance 1a between an end of the heat generating element nearer to the discharge opening and an end of the bubble nearer to the discharge opening and a distance 1b between an end of the heat generating element remote from the discharge opening and an end of the bubble remote from the discharge opening may be selected to 1a/1bxe2x89xa71.
Further, after the bubble was communicated with the atmosphere, the movable member may repel the atmosphere out of the discharge opening.
In order to discharge the bubble in the liquid into the atmosphere after the bubble was communicated with the atmosphere, the movable member may be displaced by generating a bubble not contributing to the liquid discharging.
Further, in order to prevent the bubble from remaining in the liquid, the atmosphere may be released by a tapered portion provided in the vicinity of the free end of the movable member when the movable member is returned to its initial condition.
The present invention may provide a liquid discharging head comprising a first liquid passage communicated with a discharge opening, a second liquid passage having a bubble generating area, and a movable member disposed between the first liquid passage and the bubble generating area, and wherein the movable member is displaced by generating a bubble in the bubble generating area so that the bubble is guided toward the discharge opening while regulating growth of the bubble.
In this case, the liquid supplied to the first liquid passage may be the same as the liquid supplied to the second liquid passage.
Alternatively, the liquid supplied to the first liquid passage may differ from the liquid supplied to the second liquid passage.
Further, a heat generating element for generating the bubble in the liquid may be provided at a position confronting to the movable member, and the bubble generating area may be defined between the movable member and the heat generating element.
In this case, a free end of the movable member may be situated at a downstream side of a center of an area of the heat generating element in a liquid flowing direction.
Further, stepped portions for defining a recess extending from the heat generating element toward an upstream direction may be formed on a substrate on which the heat generating elements are disposed, by pattern-etching, and a second heat generating element may be disposed on an inclined surface defining the stepped portions and inclining toward the discharge opening.
The present invention provides a liquid discharging head capable of performing the above-mentioned liquid discharging method. The liquid discharging head serves to discharge liquid by communicating a bubble generated in the liquid at an area of a discharge opening by growing the bubble and has a movable member having a free end for guiding the bubble toward the discharge opening while controlling the growth of the bubble as the bubble is growing.
When the bubble is communicated with the atmosphere, a liquid passage communicated with a liquid supply source to receive the liquid from the liquid supply source may not be blocked by the bubble.
Further, the bubble may be communicated with the atmosphere in a condition that inner pressure of the bubble is lower than the atmospheric pressure.
In addition, a heat generating element for generating the bubble in the liquid may be used, and the bubble generated in the liquid by the heat generating element may be communicated with the atmosphere through the discharge opening under a condition that a distance 1a between an end of the heat generating element nearer to the discharge opening and an end of the bubble nearer to the discharge opening and a distance 1b between an end of the heat generating element remote from the discharge opening and an end of the bubble remote from the discharge opening may be selected to 1a/1bxe2x89xa71.
Further, after the bubble was communicated with the atmosphere, the movable member may repel the atmosphere out of the discharge opening.
In order to prevent the bubble from remaining in the liquid, the atmosphere may be released by a tapered portion provided in the vicinity of the free end of the movable member when the movable member is returned to its initial condition.
The present invention also provides a liquid discharging head comprising a first liquid passage communicated with a discharge opening, a second liquid passage having a bubble generating area, and a movable member disposed between the first liquid passage and the bubble generating area, and wherein the movable member is displaced by a bubble generated in the bubble generating area so that the bubble is guided toward the discharge opening while regulating growth of the bubble.
In this case, the liquid supplied to the first liquid passage may be the same as the liquid supplied to the second liquid passage.
Alternatively, the liquid supplied to the first liquid passage may differ from the liquid supplied to the second liquid passage.
Further, a heat generating element for generating the bubble in the liquid may be provided at a position confronting to the movable member, and the bubble generating area may be defined between the movable member and the heat generating element.
In this case, a free end of the movable member may be situated at a downstream side of a center of an area of the heat generating element in a liquid flowing direction.
Further, stepped portions for defining a recess extending from the heat generating element toward an upstream direction may be formed on a substrate on which the heat generating elements are disposed, by pattern-etching, and a second heat generating element may be disposed on an inclined surface defining the stepped portions and inclining toward the discharge opening.
The present invention provides a head cartridge comprising a liquid discharging head having the above-mentioned construction, and a liquid container for containing liquid to be supplied to the liquid discharging head.
In this case, when a liquid discharging head having a first liquid passage and a second liquid passage is used, the head cartridge may include the liquid discharging head, and a liquid container for containing liquid to be supplied to the first liquid passage and liquid to be supplied to the second liquid passage.
The present invention further provides a recording apparatus comprising a liquid discharging head having the above-mentioned construction, and a drive signal supplying means for supplying a drive signal for discharging the liquid from the liquid discharging head.
The recording apparatus may include a recording medium conveying means for conveying a recording medium for receiving the liquid discharged from the liquid discharging head.
The present invention provides a head kit comprising a liquid discharging head having the above-mentioned construction, and a liquid container for containing liquid to be supplied to the liquid discharging head.
As mentioned above, the growing direction of the bubble can be directed toward the discharge opening by the movable member for controlling the growing direction of the bubble, thereby improving the discharging efficiency. Further, since the returning direction (to the initial condition) of the movable member after the liquid discharging coincides with a liquid re-filling direction, re-filling frequency and discharge repeating frequency can be increased, thereby permitting high speed recording.
Incidentally, in the specification and claims, the terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d are referred to regarding the liquid flowing direction from the liquid supply source through the bubble generating area (or movable member) to the discharge opening, or the constructural direction.
Further, the term xe2x80x9cdownstream sidexe2x80x9d regarding the bubble itself mainly means a discharge opening side portion of the bubble directly relating the liquid discharging. More particularly, it means a bubble portion generated at a downstream of a center of the bubble in the liquid flowing direction or the constructural direction or at downstream of a center of the area of the heat generating element.
In addition, the term xe2x80x9cseparation wallxe2x80x9d means a wall (which may include the movable member) disposed to separate the bubble generating area from a area directly communicated with the discharge opening in a broader sense, and means a wall for distinguishing the liquid passage including the bubble generating area from the liquid passage directly communicated with the discharge opening and for preventing the mixing of the liquids in both liquid passages in a narrower sense.